Human lysophosphatidic acid receptor and use thereof

ABSTRACT

(1) A human lysophosphatidic acid (human LPA) receptor, (2) a method for screening an antagonist or agonist, comprising using a human LPA receptor protein, (3) an LPA inhibitor comprising the human LPA receptor, (4) a method for producing the human LPA receptor, (5) a monoclonal or polyclonal antibody against the human LPA receptor, (6) a cDNA encoding the human LPA receptor, (7) a replication or expression vector carrying the above cDNA, and (8) a host cell transformed with the above replication or expression vector.

TECHNICAL FIELD

The present invention relates to a lysophosphatidic acid (LPA) receptor and use thereof. More specifically, it relates to (1) a human LPA receptor, (2) a method for screening a human LPA-like substance, a human LPA antagonist and an antagonist or agonist for a phospholipid other than LPA capable of responding to the human LPA receptor, comprising using a human LPA receptor protein, (3) an LPA inhibitor or an inhibitor for a phospholipid other than human LPA, comprising the human LPA receptor, (4) a method for producing the human LPA receptor, (5) a monoclonal or polyclonal antibody against the human LPA receptor, (6) a cDNA encoding the human LPA receptor, (7) a replication or expression vector carrying the above cDNA, and (8) a host cell transformed with the above replication or expression vector.

BACKGROUND ART

It is known that LPA receptors bind LPA to transmit a signal into cells and induce various physiological phenomena, such as cell proliferation, dedifferentiation of vascular cells, inhibition of cell proliferation, and the like. Thus, if a human LPA receptor can be provided, not only its application as a medicament or diagnostic drug for vasospasm and the like can be expected using the human LPA receptor per se but also its broad contribution to the development of medicaments, such as screening and evaluation of medicaments, such as a new LPA receptor antagonist and the like, can be expected. Although it is known that plural kinds of LPA receptors are present, all kinds of human LPA receptors have not been isolated yet, and the actions and structures have not been specified.

Cells recognize various physiologically active substances, such as proliferation factors, hormones, neurotransmitters, and the like, via a receptor and response thereto in various manner. LPA receptors which are present on the cell membrane bind to LPA and transmit a signal into the cell via a G protein conjugated with the receptor. Gi, Gq and the like are known as G proteins which can be conjugated with LPA receptors, and it is considered that these receptors take part in responses, such as cell proliferation promoting action or, conversely, proliferation inhibiting action, and the like. Additionally, it has been found that an MAP-kinase system is connected with the downstream of the G protein and the LPA receptors transmit various signals.

Receptors using LPA as the ligand have been isolated from mouse and Xenopus. For example, Tigyi et al. have obtained an LPA receptor, called PSP24 LPA receptor, for the first time from Xenopus oocyte (Proc. Natl. Acad. Sci. U.S.A., 93: 14367-14372 (1996)). Also, another kind of LPA receptor has been cloned from a mouse, which is called vzg-1 (J. Cell. Biol., 135:1071-1083 (1996)).

As human origin LPA receptors, Edg-2 which is a homologue of vzg-1 has been reported (Biochem. Bioph. Res. Commun., 231:619-622 (1997)); however, there are no reports on the PSP24 in human.

SUMMARY OF THE INVENTION

With the aim of cloning a human counterpart of the PSP24 LPA receptor which is expressed in Xenopus oocyte, the present inventors have conducted intensive studies and, as a result, succeeded in cloning a cDNA encoding a PSP24 human LPA receptor derived from a human brain tissue and in determining the complete amino acid sequence of the LPA receptor.

When the known nucleotide sequences registered in the nucleotide sequence database were searched by BLASTN, and the amino acid sequences of known polypeptides registered in the amino acid sequence database by BLASTP, there was no sequence which coincided with the nucleotide sequence encoding the PSP24 human LPA receptor. Also, it was expected based on a hydrophobic plotting analysis that the polypeptide of the LPA receptor has seven transmembrane domains. Accordingly, it was confirmed that this polypeptide is a novel membrane protein.

The present invention relates to:

(1) a protein comprising the amino acid sequence shown in SEQ ID NO:1, a homologue thereof, a fragment thereof, or a fragment of the homologue thereof;

(2) a human lysophosphatidic acid (human LPA) receptor comprising the amino acid sequence shown in SEQ ID NO:1 or a homologue thereof;

(3) a method for screening a human LPA-like substance, a human LPA antagonist, and an antagonist or agonist for a phospholipid other than LPA capable of responding to the human LPA receptor, comprising using the protein according to the above (1) or (2);

(4) a human LPA inhibitor or an inhibitor for a phospholipid other than human LPA, comprising the protein according to the above (1) or (2) as an active ingredient;

(5) a method for producing a human LPA receptor, comprising culturing a cell transformed with an expression vector carrying a DNA fragment encoding the protein according to the above (1) or (2), and recovering the protein from the cultured mixture;

(6) a monoclonal or polyclonal antibody against the protein according to the above (1) or (2) or a peptide comprising a partial sequence of the protein;

(7) a cDNA encoding the polypeptide according to the above (1) or (2);

(8) a fragment which selectively hybridizes to the cDNA according to the above (7) comprising the nucleotide sequence shown in SEQ ID NO:2, or a sequence thereof;

(9) a fragment which selectively hybridizes to the cDNA according to the above (7) comprising the nucleotide sequence shown in SEQ ID NO:3, or a sequence thereof;

(10) a replication or expression vector carrying the cDNA according to any one of the above (6) to (9); and

(11) a host cell transformed with the replication or expression vector according to the above (10).

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a result of Northern hybridization of the expression of human LPA receptor of the present invention in CHO cells.

DETAILED DESCRIPTION

The present invention relates to a polypeptide shown in SEQ ID NO:1 in substantially purified form, a homologue thereof, a fragment of the sequence, and a homologue thereof.

Furthermore, the present invention relates to a cDNA encoding these polypeptides. More specifically, it relates to the nucleotide sequence shown in SEQ ID NO:2.

A complementary sequence of the above sequence is also included in the cDNA to be hybridized.

It is preferred that the hybridization conditions are stringent.

The homologue of the polypeptide comprising the amino acid sequence shown in SEQ ID NO:1 is a contiguous amino acid region of usually at least 20 amino acids, preferably at least 30 amino acids, for example 40, 60 or 100 amino acids, which has a homology of at least 70%, preferably at least 80 or 90%, more preferably at least 95%. Such a homologue is hereinafter referred to as the polypeptide of the present invention.

Also, the fragment of the polypeptide comprising the amino acid sequence shown in SEQ ID NO:1 or a fragment of its homologue is a region of at least 10 amino acids, preferably at least 15 amino acid, for example 20, 25, 30, 40, 50 or 60 amino acids.

The cDNA which selectively hybridizes to the CDNA having the nucleotide sequence shown in SEQ ID NO:2 or 3 is a contiguous nucleotide sequence region of usually at least 20 nucleotides, preferably at least 30 nucleotides, for example 40, 60 or 100 nucleotides, which has a homology of at least 70%, preferably at least 80 or 90%, more preferably at least 95%. Such a cDNA is hereinafter referred to as the cDNA of the present invention.

The fragment of the cDNA comprising the nucleotide sequence shown in SEQ ID NO:2 is a contiguous nucleotide sequence region of at least 10 nucleotides, preferably at least 15 nucleotides, for example 20, 25, 30 or 40 nucleotides. Such a fragment is also included in the cDNA of the present invention.

Moreover, the present invention also includes a method for producing the polypeptide of the present invention, comprising culturing the host cell of the present invention under conditions for expressing the polypeptide of the present invention. Preferably, the culturing is carried out under such conditions that the polypeptide of the present invention is expressed and produced by the host cell.

The cDNA of the present invention can produce an antisense mRNA by inserting it into the anfisense region of the above-described vector. Such an antisense mRNA can be used for controlling the level of the polypeptide of the present invention in cells.

The present invention also includes a monoclonal or polyclonal antibody against the polypeptide of the present invention. The present invention also includes a method for producing a monoclonal or polyclonal antibody against the polypeptide of the present invention. The monoclonal antibody can be produced by usual hybridoma techniques using the peptide of the present invention or its fragment as the antigen. The polyclonal antibody can be produced by a general method in which the polypeptide of the present invention is inoculated into a host animal (e.g., rat, rabbit etc.), and the immunized serum is recovered.

The present invention also includes a pharmaceutical composition comprising the polypeptide of the present invention or its antibody and a pharmaceutically acceptable excipient and/or carrier.

In addition to the polypeptide comprising the amino acid sequence shown in SEQ ID NO:1, the polypeptide of the present invention includes those in which a part thereof is deleted (e.g., a polypeptide consisting of only a portion of the SEQ ID NO:1, which is essential for the expression of a biological activity etc.), those in which a portion thereof is substituted with other amino acid (e.g., substituted with an amino acid having a similar physical property), and those in which an amino acid is added to or inserted into a portion thereof.

As is commonly known, 1 to 6 codons encode one amino acid (e.g., one codon for Met, and 6 codons for Leu). Therefore, the nucleotide sequence of the cDNA can be changed without changing the amino acid sequence of the polypeptide.

All of the nucleotide sequences encoding the polypeptide shown in SEQ ID NO:1 are included in the cDNA of the present invention. Productivity of the polypeptide may be improved by changing the nucleotide sequence.

The cDNA shown in the SEQ ID NO:2 is an embodiment of the CDNA of the present invention and represents a native sequence.

The cDNA shown in SEQ ID NO:3 is a sequence in which a native non-translation moiety is added to the cDNA shown in the SEQ ID NO.2.

The CDNA comprising the nucleotide sequence shown in the SEQ ID NO:2 or 3 can be produced, for example, according to the following method. cDNA Cloning of Human LPA Receptor:

Generally, poly(A)⁺ RNA can be produced by extracting total mRNA from an adult human brain tissue, a human kidney tissue, or the like or from various human cell strains, using a TRIzol reagent (trade name, available from GIBCO BRL) or the like, and by purifying it using a mRNA Purification Kit (trade name, available from Pharmacia) or the like. A cDNA is produced using the method of Gubler et al. (Gene, 25:263 (1983)) or a commercially available cDNA synthesis kit, followed by optionally separating a long base pair, and can be introduced into a plasmid vector (e.g., pUC19) or a λ phage vector (e.g., λgt11).

By carrying out screening of the thus prepared cDNA library by colony hybridization or plaque hybridization using a labeled probe in the usual way, a clone comprising a cDNA fragment containing a region encoding the entire portion of PSP24 human LPA receptor or a part thereof can be selected. Furthermore, optionally, a PSP24 human LPA receptor cDNA can be isolated by again cloning the cDNA into other vector. As a method completely different from this, a partial length of the PSP24 human LPA receptor cDNA can be cloned by PCR by producing primers from the cDNA prepared in the above-described manner, based on the cDNA sequence isolated from Xenopus, and cloning of the complete length can be carried out making use thereof.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is illustratively described in the following with reference to examples, but they do not limit the scope of the present invention.

Example 1: Preparation of poly(A)⁺ RNA and cDNA

Total RNA was extracted from an adult human brain tissue using TRizol reagent (trade name, available from GIBCO BRL), and poly(A)⁺ RNA was purified using mRNA Purification Kit (trade name, available from Pharmacia).

Based on the poly(A)⁺ RNA, a cDNA was synthesized using Marathon cDNA Amplification Kit (trade name, available from Clontech).

Example 2: Partial Cloning of PSP24 Human LPA Receptor

Based on the information of nucleotide sequences corresponding to the LPA receptor (PSP24) obtained from Xenopus oocyte, 18 sense primers and the same number of antisense primers were produced, and PCR was carried out among these primers. A band seemed to be a partial fragment of human PSP24 clone was amplified by a combination of certain primers among them. The primer set used in this PCR is shown below.

Xenopus PSP24 Primer #15:

5′-TTCCTTATTATTGTACAGAGGCAGG-3′(25 mer) (SEQ ID NO:4),

Xenopus PSP24 Primer #21:

5′-AAGAGMTCAAAATAGTGGTGAAGG-3′(25 mer) (SEQ ID NO:5).

The thus amplified cDNA was fractionated by agarose electrophoresis, linked to pT7Blue-2 T-Vector (trade name, available from Novagen) and then transformed into Escherichia coli DH5a to produce a plasmid. Thereafter, the complete nucleotide sequence of this DNA was determined. When the known nucleotide sequences registered in the nucleotide sequence database were searched for the thus determined nucleotide sequence by BLASTN, and the amino acid sequences of known polypeptides registered in the amino acid sequence database were searched for the amino acid sequence translated from the thus determined nucleotide sequence by BLASTP, there was no sequence which showed homology with the Xenopus PSP24 LPA receptor and coincided with the thus determined nucleotide sequence of DNA and amino acid sequence. Accordingly, it was confirmed that this PCR product is a partial length of a novel gene.

Example 3: Complete Length Cloning of PSP24 Human LPA Receptor

Next, complete length cloning was attempted using Marathon cDNA Amplification Kit (trade name, available from Clontech). New primers (F1, F2, F3, R1, R2 and R3) were produced based on the thus determined partial length nucleotide sequence, and 5′-RACE (rapid amplification of cDNA ends) and 3′-RACE were carried out between these primers and 5′-side or 3′-side adapter sequence-specific primers (AP1 and AP2). A band seemed to be a 5′-moiety or 3′-moiety of the PSP24 human LPA receptor clone was amplified by the following combinations of primers among them. The primer sets used in this PCR are shown below.

1st PCR Nested PCR 5′-RACE R1-AP1 R2-AP2 R2-AP1 R3-AP2 R3-AP1 R3-AP2 3′-RACE 1-AP1 F2-AP2 2-AP1 F3-AP2

R1 primer:

5′-GCCCATGTCAATGCTCATCTGGAAAGG-3′(27 mer) (SEQ ID NO:6),

R2 primer:

5′-AGGTCTCTGCAGACTCATGAGACCCAG-3′(27 mer) (SEQ ID NO:7),

R3 primer:

5′-GCTGGCCTGGCTGAGGCATATACCTTC-3′(27 mer) (SEQ ID NO:8),

F1 primer:

5′-GTCCAGAGGCAGGATAAGCTAAACCCA-3′(27 mer) (SEQ ID NO:9),

F2 primer:

5′-CCGACCTGCAGATACCTTCCCGAGCTC-3′(27 mer) (SEQ ID NO:10),

F3 primer:

5′-ACCAATCCAGGCTACCAGGCTTATGTG-3′(27 mer) (SEQ ID NO:11)

AP1 primer:

5′-CCATCCTAATACGACTCACTATAGGGC-3′(27 mer) (SEQ ID NO:12):

AP2 primer:

5′-ACTCACTATAGGGCTCGAGCGGC-3′(23 mer) (SEQ ID NO:13).

By subcloning the thus amplified cDNA in the same manner as the partial cloning, the complete nucleotide sequence was determined to obtain the sequence shown in SEQ ID NO:3. Thereafter, the open reading frame was determined and translated into amino acids to obtain the sequence shown in SEQ ID NO:1. When the known nucleotide sequences registered in the nucleotide sequence database were searched by BLASTN, and the amino acid sequences of known polypeptides registered in the amino acid sequence database by BLASTP, there was no sequence which coincided with the nucleotide sequence encoding the polypeptide of the present invention, the PSP24 human LPA receptor. Accordingly, it was confirmed that the polypeptide of the present invention is a novel membrane protein. Also, since there was no homology with similar membrane proteins having seven transmembrane domains, such as PAF receptor, LTB4 receptor and the like, a possibility was suggested that this clone is a human counterpart of the Xenopus PSP24 LPA receptor.

Example 4: Cloning of Complete Length CDNA and Determination of Nucleotide Sequence

Cloning of a complete length cDNA was carried out by PCR by producing primers based on the thus determined nucleotide sequence of the PSP24 human LPA receptor shown in SEQ ID NO:3 so as to contain the Kozac sequence and the total translation region. The following two primers were used.

5′-Side Primer:

5′-AAACCATGGTCTTCTCGGCAGTGTTGA-3′(27 mer) (SEQ ID NO:14),

3′-Side Primer:

5′-TCACACCACCGTCCGATGTTCCCCACA-3′(27 mer) (SEQ ID NO:15).

By subcloning the specifically amplified cDNA in the same manner as the partial cloning, the complete nucleotide sequence was determined to obtain the sequence shown in SEQ ID NO:1. Thereafter, the open reading frame was determined and the complete length was isolated.

Example 5: Expression of Protein in Mammal Cells

The receptor of the present invention (PSP24 human LPA receptor) was introduced into CHO cells using a lipofection method to obtain stably character-expressing cells. In order to maximize the receptor expression, the gene was introduced into a vector having a blasticidin-resistant marker, made into a straight chain and then introduced into the cells. Next, the cells were cultured in the presence of blasticidin (5 μg/ml), and 29 resistant strains were isolated by a limiting dilution method. Total RNA was prepared from these clones using TRIzol reagent (Gibco BRL), and expressing clones were selected by RT-PCR. Strength of expression by the expression-confirmed clones was measured by Northern hybridization using the complete length of the gene as a probe (FIG. 1). The numeral shown in the light-side of the drawing indicates the size of a ribosomal RNA used as a size marker, and a band considered to be a transcription product of the gene was observed at around 1.9 kb. As a control, electrophoresis of the total RNA prepared from CHO cells of the parent strain was carried out and shown in the left-side end.

15 1 419 PRT Homo sapiens 1 Met Val Phe Ser Ala Val Leu Thr Ala Phe His Thr Gly Thr Ser Asn 1 5 10 15 Thr Thr Phe Val Val Tyr Glu Asn Thr Tyr Met Asn Ile Thr Leu Pro 20 25 30 Pro Pro Phe Gln His Pro Asp Leu Ser Pro Leu Leu Arg Tyr Ser Phe 35 40 45 Glu Thr Met Ala Pro Thr Gly Leu Ser Ser Leu Thr Val Asn Ser Thr 50 55 60 Ala Val Pro Thr Thr Pro Ala Ala Phe Lys Ser Leu Asn Leu Pro Leu 65 70 75 80 Gln Ile Thr Leu Ser Ala Ile Met Ile Phe Ile Leu Phe Val Ser Phe 85 90 95 Leu Gly Asn Leu Val Val Cys Leu Met Val Tyr Gln Lys Ala Ala Met 100 105 110 Arg Ser Ala Ile Asn Ile Leu Leu Ala Ser Leu Ala Phe Ala Asp Met 115 120 125 Leu Leu Ala Val Leu Asn Met Pro Phe Ala Leu Val Thr Ile Leu Thr 130 135 140 Thr Arg Trp Ile Phe Gly Lys Phe Phe Cys Arg Val Ser Ala Met Phe 145 150 155 160 Phe Trp Leu Phe Val Ile Glu Gly Val Ala Ile Leu Leu Ile Ile Ser 165 170 175 Ile Asp Arg Phe Leu Ile Ile Val Gln Arg Gln Asp Lys Leu Asn Pro 180 185 190 Tyr Arg Ala Lys Val Leu Ile Ala Val Ser Trp Ala Thr Ser Phe Cys 195 200 205 Val Ala Phe Pro Leu Ala Val Gly Asn Pro Asp Leu Gln Ile Pro Ser 210 215 220 Arg Ala Pro Gln Cys Val Phe Gly Tyr Thr Thr Asn Pro Gly Tyr Gln 225 230 235 240 Ala Tyr Val Ile Leu Ile Ser Leu Ile Ser Phe Phe Ile Pro Phe Leu 245 250 255 Val Ile Leu Tyr Ser Phe Met Gly Ile Leu Asn Thr Leu Arg His Asn 260 265 270 Ala Leu Arg Ile His Ser Tyr Pro Glu Gly Ile Cys Leu Ser Gln Ala 275 280 285 Ser Lys Leu Gly Leu Met Ser Leu Gln Arg Pro Phe Gln Met Ser Ile 290 295 300 Asp Met Gly Phe Lys Thr Arg Ala Phe Thr Thr Ile Leu Ile Leu Phe 305 310 315 320 Ala Val Phe Ile Val Cys Trp Ala Pro Phe Thr Thr Tyr Ser Leu Val 325 330 335 Ala Thr Phe Ser Lys His Phe Tyr Tyr Gln His Asn Phe Phe Glu Ile 340 345 350 Ser Thr Trp Leu Leu Trp Leu Cys Tyr Leu Lys Ser Ala Leu Asn Pro 355 360 365 Leu Ile Tyr Tyr Trp Arg Ile Lys Lys Phe His Asp Ala Cys Leu Asp 370 375 380 Met Met Pro Lys Ser Phe Lys Phe Leu Pro Gln Leu Pro Gly His Thr 385 390 395 400 Lys Arg Arg Ile Arg Pro Ser Ala Val Tyr Val Cys Gly Glu His Arg 405 410 415 Thr Val Val 2 1257 DNA Homo sapiens 2 atggtcttct cggcagtgtt gactgcgttc cataccggga catccaacac aacatttgtc 60 gtgtatgaaa acacctacat gaatattaca ctccctccac cattccagca tcctgacctc 120 agtccattgc ttagatatag ttttgaaacc atggctccca ctggtttgag ttccttgacc 180 gtgaatagta cagctgtgcc cacaacacca gcagcattta agagcctaaa cttgcctctt 240 cagatcaccc tttctgctat aatgatattc attctgtttg tgtcttttct tgggaacttg 300 gttgtttgcc tcatggttta ccaaaaagct gccatgaggt ctgcaattaa catcctcctt 360 gccagcctag cttttgcaga catgttgctt gcagtgctga acatgccctt tgccctggta 420 actattctta ctacccgatg gatttttggg aaattcttct gtagggtatc tgctatgttt 480 ttctggttat ttgtgataga aggagtagcc atcctgctca tcattagcat agataggttc 540 cttattatag tccagaggca ggataagcta aacccatata gagctaaggt tctgattgca 600 gtttcttggg caacttcctt ttgtgtagct tttcctttag ccgtaggaaa ccccgacctg 660 cagatacctt cccgagctcc ccagtgtgtg tttgggtaca caaccaatcc aggctaccag 720 gcttatgtga ttttgatttc tctcatttct ttcttcatac ccttcctggt aatactgtac 780 tcatttatgg gcatactcaa cacccttcgg cacaatgcct tgaggatcca tagctaccct 840 gaaggtatat gcctcagcca ggccagcaaa ctgggtctca tgagtctgca gagacctttc 900 cagatgagca ttgacatggg ctttaaaaca cgtgccttca ccactatttt gattctcttt 960 gctgtcttca ttgtctgctg ggccccattc accacttaca gccttgtggc aacattcagt 1020 aagcactttt actatcagca caactttttt gagattagca cctggctact gtggctctgc 1080 tacctcaagt ctgcattgaa tccgctgatc tactactgga ggattaagaa attccatgat 1140 gcttgcctgg acatgatgcc taagtccttc aagtttttgc cgcagctccc tggtcacaca 1200 aagcgacgga tacgtcctag tgctgtctat gtgtgtgggg aacatcggac ggtggtg 1257 3 1892 DNA Homo sapiens CDS (208)..(1464) 3 tggagccatg ctccctgggc tcttccgcgg gcgcccgcgc gctgcccttc gcttgaggca 60 aaaggactct tgtggaagat ggaactcatt gtccattttc cagaatgtat ttccaagccc 120 atcaatggga cctgatactg ctgttctgtg ttgaaatgct tgaagaactc ctgcatctct 180 gcttgcatct tccatcctac tgaaacc atg gtc ttc tcg gca gtg ttg act gcg 234 Met Val Phe Ser Ala Val Leu Thr Ala 1 5 ttc cat acc ggg aca tcc aac aca aca ttt gtc gtg tat gaa aac acc 282 Phe His Thr Gly Thr Ser Asn Thr Thr Phe Val Val Tyr Glu Asn Thr 10 15 20 25 tac atg aat att aca ctc cct cca cca ttc cag cat cct gac ctc agt 330 Tyr Met Asn Ile Thr Leu Pro Pro Pro Phe Gln His Pro Asp Leu Ser 30 35 40 cca ttg ctt aga tat agt ttt gaa acc atg gct ccc act ggt ttg agt 378 Pro Leu Leu Arg Tyr Ser Phe Glu Thr Met Ala Pro Thr Gly Leu Ser 45 50 55 tcc ttg acc gtg aat agt aca gct gtg ccc aca aca cca gca gca ttt 426 Ser Leu Thr Val Asn Ser Thr Ala Val Pro Thr Thr Pro Ala Ala Phe 60 65 70 aag agc cta aac ttg cct ctt cag atc acc ctt tct gct ata atg ata 474 Lys Ser Leu Asn Leu Pro Leu Gln Ile Thr Leu Ser Ala Ile Met Ile 75 80 85 ttc att ctg ttt gtg tct ttt ctt ggg aac ttg gtt gtt tgc ctc atg 522 Phe Ile Leu Phe Val Ser Phe Leu Gly Asn Leu Val Val Cys Leu Met 90 95 100 105 gtt tac caa aaa gct gcc atg agg tct gca att aac atc ctc ctt gcc 570 Val Tyr Gln Lys Ala Ala Met Arg Ser Ala Ile Asn Ile Leu Leu Ala 110 115 120 agc cta gct ttt gca gac atg ttg ctt gca gtg ctg aac atg ccc ttt 618 Ser Leu Ala Phe Ala Asp Met Leu Leu Ala Val Leu Asn Met Pro Phe 125 130 135 gcc ctg gta act att ctt act acc cga tgg att ttt ggg aaa ttc ttc 666 Ala Leu Val Thr Ile Leu Thr Thr Arg Trp Ile Phe Gly Lys Phe Phe 140 145 150 tgt agg gta tct gct atg ttt ttc tgg tta ttt gtg ata gaa gga gta 714 Cys Arg Val Ser Ala Met Phe Phe Trp Leu Phe Val Ile Glu Gly Val 155 160 165 gcc atc ctg ctc atc att agc ata gat agg ttc ctt att ata gtc cag 762 Ala Ile Leu Leu Ile Ile Ser Ile Asp Arg Phe Leu Ile Ile Val Gln 170 175 180 185 agg cag gat aag cta aac cca tat aga gct aag gtt ctg att gca gtt 810 Arg Gln Asp Lys Leu Asn Pro Tyr Arg Ala Lys Val Leu Ile Ala Val 190 195 200 tct tgg gca act tcc ttt tgt gta gct ttt cct tta gcc gta gga aac 858 Ser Trp Ala Thr Ser Phe Cys Val Ala Phe Pro Leu Ala Val Gly Asn 205 210 215 ccc gac ctg cag ata cct tcc cga gct ccc cag tgt gtg ttt ggg tac 906 Pro Asp Leu Gln Ile Pro Ser Arg Ala Pro Gln Cys Val Phe Gly Tyr 220 225 230 aca acc aat cca ggc tac cag gct tat gtg att ttg att tct ctc att 954 Thr Thr Asn Pro Gly Tyr Gln Ala Tyr Val Ile Leu Ile Ser Leu Ile 235 240 245 tct ttc ttc ata ccc ttc ctg gta ata ctg tac tca ttt atg ggc ata 1002 Ser Phe Phe Ile Pro Phe Leu Val Ile Leu Tyr Ser Phe Met Gly Ile 250 255 260 265 ctc aac acc ctt cgg cac aat gcc ttg agg atc cat agc tac cct gaa 1050 Leu Asn Thr Leu Arg His Asn Ala Leu Arg Ile His Ser Tyr Pro Glu 270 275 280 ggt ata tgc ctc agc cag gcc agc aaa ctg ggt ctc atg agt ctg cag 1098 Gly Ile Cys Leu Ser Gln Ala Ser Lys Leu Gly Leu Met Ser Leu Gln 285 290 295 aga cct ttc cag atg agc att gac atg ggc ttt aaa aca cgt gcc ttc 1146 Arg Pro Phe Gln Met Ser Ile Asp Met Gly Phe Lys Thr Arg Ala Phe 300 305 310 acc act att ttg att ctc ttt gct gtc ttc att gtc tgc tgg gcc cca 1194 Thr Thr Ile Leu Ile Leu Phe Ala Val Phe Ile Val Cys Trp Ala Pro 315 320 325 ttc acc act tac agc ctt gtg gca aca ttc agt aag cac ttt tac tat 1242 Phe Thr Thr Tyr Ser Leu Val Ala Thr Phe Ser Lys His Phe Tyr Tyr 330 335 340 345 cag cac aac ttt ttt gag att agc acc tgg cta ctg tgg ctc tgc tac 1290 Gln His Asn Phe Phe Glu Ile Ser Thr Trp Leu Leu Trp Leu Cys Tyr 350 355 360 ctc aag tct gca ttg aat ccg ctg atc tac tac tgg agg att aag aaa 1338 Leu Lys Ser Ala Leu Asn Pro Leu Ile Tyr Tyr Trp Arg Ile Lys Lys 365 370 375 ttc cat gat gct tgc ctg gac atg atg cct aag tcc ttc aag ttt ttg 1386 Phe His Asp Ala Cys Leu Asp Met Met Pro Lys Ser Phe Lys Phe Leu 380 385 390 ccg cag ctc cct ggt cac aca aag cga cgg ata cgt cct agt gct gtc 1434 Pro Gln Leu Pro Gly His Thr Lys Arg Arg Ile Arg Pro Ser Ala Val 395 400 405 tat gtg tgt ggg gaa cat cgg acg gtg gtg tgaatattgg aactggctga 1484 Tyr Val Cys Gly Glu His Arg Thr Val Val 410 415 cattttgggt gatgcttgtt ctttattgac attgaattct ctttctcata gcctctccac 1544 tttatttttt tttatagggt ttgtgtatgt atgtgtgtga gcagtgtaaa gaaagaatgg 1604 taattatagt tctgttacca agaataaata ataggaaagt gattacaaat attacctcca 1664 gggttcaata gaaatcctca atttagggtg aggagacttt tttttggttt tggggttttt 1724 ccttgattga ttttgttttc atagtgggaa tcaggattgt gctttattga gcctgcagtt 1784 acattgaatt gtaggtgttt cgtgtgctgc taaggtatgc ttatttgagt ttatcaagac 1844 tttttttttt ctggaagaca ctgctgcttt taccatcaca ttggagcc 1892 4 25 DNA Xenopus laeuis PSP24 primer #15 4 ttccttatta ttgtacagag gcagg 25 5 25 DNA Xenopus laeuis PSP24 primer #21 5 aagagaatca aaatagtggt gaagg 25 6 27 DNA Artificial Sequence Description of Artificial Sequence R1 primer 6 gcccatgtca atgctcatct ggaaagg 27 7 27 DNA Artificial Sequence Description of Artificial Sequence R2 primer 7 aggtctctgc agactcatga gacccag 27 8 27 DNA Artificial Sequence Description of Artificial Sequence R3 primer 8 gctggcctgg ctgaggcata taccttc 27 9 27 DNA Artificial Sequence Description of Artificial Sequence F1 primer 9 gtccagaggc aggataagct aaaccca 27 10 27 DNA Artificial Sequence Description of Artificial Sequence F2 primer 10 ccgacctgca gataccttcc cgagctc 27 11 27 DNA Artificial Sequence Description of Artificial Sequence F3 primer 11 accaatccag gctaccaggc ttatgtg 27 12 27 DNA Unknown Description of Unknown Sequence 5′Race adaptor primer AP1 primer 12 ccatcctaat acgactcact atagggc 27 13 23 DNA Unknown Description of Unknown Sequence 3′Race adaptor primer AP1 primer 13 actcactata gggctcgagc ggc 23 14 27 DNA Artificial Sequence Description of Artificial Sequence 5′end primer coding kozac sequence and all transcription region of PSP24 type human lysophosphatidic acid receptor 14 aaaccatggt cttctcggca gtgttga 27 15 27 DNA Artificial Sequence Description of Artificial Sequence 3′end primer coding kozac sequence and all transcription region of PSP24 type human lysophosphatidic acid receptor 15 tcacaccacc gtccgatgtt ccccaca 27 

What is claimed is:
 1. A protein comprising the amino acid sequence shown in SEQ ID No:1.
 2. A human lysophosphatidic acid (human LPA) receptor comprising the amino acid sequence shown in SEQ ID NO:1.
 3. A method for screening a human LPA-like substance, a human LPA antagonist, and an antagonist or agonist for a phospholipid other than LPA capable of responding to the human LPA receptor, comprising using the protein according to claim 1 or
 2. 4. A human LPA inhibitor or an inhibitor for a phospholipid other than human LPA, comprising the protein according to claim 1 or 2 as an active ingredient.
 5. A method for producing a human LPA receptor, comprising culturing a cell transformed with an expression vector carrying a DNA fragment encoding the protein according to claim 1 or 2, and recovering the protein from the cultured mixture.
 6. A monoclonal or polyclonal antibody which specifically binds to the protein according to claims 1 and
 2. 7. A cDNA encoding the polypeptide comprising the amino sequence shown in SEQ ID NO:1.
 8. A CDNA according to claim 7 comprising the nucleotide sequence shown in SEQ ID NO:2.
 9. A cDNA according to claim 7 comprising the nucleotide sequence shown in SEQ ID NO:3.
 10. A replication or expression vector carrying the cDNA according to any one of claims 7 to
 9. 11. A host cell transformed with the replication or expression vector according to claim
 10. 